PULLMAN, Wash. Since 1999, a virulent new wheat disease discovered in research plots in Uganda has spread through Kenya, Ethiopia, and the Sudan as well as across the Red Sea to Yemen. Known as UG99, this new race of stem rust which has been able to overcome resistance genes bred into wheat varieties commonly planted around the world was reported in Iran in 2007, where prevailing winds are expected to carry the spores of the fungus to Pakistan, India and eventually, the United States.
Current estimates suggest as much as 80 percent of all wheat varieties planted in Asia and Africa, as well as a large percentage of the wheat strains grown all across the U.S., are susceptible to this new form of stem rust, a plant disease which has reached epidemic proportions in the U.S. before, most recently in 1954.
Tim Murray, a Washington State University plant pathologist, is collaborating with scientists around the world to address this latest threat to world wheat production. As chair of a committee of U.S. government and land-grant university scientists tasked with preparing a recovery plan should UG99 be introduced to the United States, he is preparing a plan to track the disease and its impact on susceptible wheat varieties once it reaches our shores.
“The real challenge will be to know when it arrives, Murray said. “You can’t tell UG99 apart from any other stem rust by looking at it. They all look alike.”
Murray says researchers already have identified sources of genetic resistance to UG99 and breeding lines with resistance are in the pipeline, but it will take several more years of breeding to put seed with multi-gene resistance into the hands of farmers
No one knows when the disease will reach the U.S., he says. Likely routes of introduction include the path that Asian soybean rust took a few years ago, where spores crossed the Atlantic from the west coast of Africa and moved north through South America. Another route could be the accidental, or even intentional, introduction by people moving to the U.S. from areas where UG99 occurs.
Murray is a professor in the Department of Plant Pathology with the WSU College of Agricultural, Human, and Natural Resource Sciences. He can be reached at 509-335-7515 or by e-mail at tim_murray@wsu.edu.
